From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: linux-nfs-owner@vger.kernel.org Received: from mail.linuxfoundation.org ([140.211.169.12]:54070 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751109Ab3HSUfE (ORCPT ); Mon, 19 Aug 2013 16:35:04 -0400 Date: Mon, 19 Aug 2013 13:35:03 -0700 From: Andrew Morton To: Jeff Layton Cc: Al Viro , linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, Neil Brown Subject: Re: [PATCH] vfs: allow umount to handle mountpoints without revalidating them Message-Id: <20130819133503.1a793ecbfa99c1b0814bbb57@linux-foundation.org> In-Reply-To: <1374834205-4406-1-git-send-email-jlayton@redhat.com> References: <1374834205-4406-1-git-send-email-jlayton@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-nfs-owner@vger.kernel.org List-ID: On Fri, 26 Jul 2013 06:23:25 -0400 Jeff Layton wrote: > Christopher reported a regression where he was unable to unmount a NFS > filesystem where the root had gone stale. The problem is that > d_revalidate handles the root of the filesystem differently from other > dentries, but d_weak_revalidate does not. We could simply fix this by > making d_weak_revalidate return success on IS_ROOT dentries, but there > are cases where we do want to revalidate the root of the fs. > > A umount is really a special case. We generally aren't interested in > anything but the dentry and vfsmount that's attached at that point. If > the inode turns out to be stale we just don't care since the intent is > to stop using it anyway. > > Try to handle this situation better by treating umount as a special > case in the lookup code. Have it resolve the parent using normal > means, and then do a lookup of the final dentry without revalidating > it. In most cases, the final lookup will come out of the dcache, but > the case where there's a trailing symlink or !LAST_NORM entry on the > end complicates things a bit. > In which kernel version did the regression occur? The patch *applies* to 3.8 and perhaps earlier, but we don't know which kernel versions actually need it.